The present invention relates to a process for the preparation of 2-tert-butyl-4-methoxyphenol.
2-Tert-butyl-4-methoxyphenol, hereinafter referred to as BHA (butylated hydroxyanisole) for the sake of brevity, is a well known preservative for food products. The process commonly employed for its preparation involves methylating hydroquinone to obtain 4-methoxyphenol which is then reacted with isobutylene to yield BHA. This process, however, presents several disadvantages. In the first reaction, dimethylation of hydroquinone also takes place, leading to an undesired by-product. The second reaction, viz., the butylation of 4-methoxyphenol, is not selective, leading to a mixture of 2- and 3-tert-butyl-4-methoxyphenol isomers, typically a mixture of 70% 2-isomer and 30% 3-isomer.
The separation of the 2- and 3-BHA isomers is expensive and very difficult, since the purification of the 2-isomer is carried out by multiple crystallization. Furthermore, BHA must contain at least 85% of the 2-isomer; commercially available products are sold with a 90-93% content of the 2-isomer. It is therefore clearly desirable to provide a process by which the useful 2-BHA isomer can be recovered in high yield and with high purity.
It is an object of the present invention to provide a simple and economic process by which substantially pure 2-BHA isomer can be prepared.